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API Master Test Kits

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Query, have any of you had any problems with these test kits? Following the instructions to the letter, I constantly show 5+ ppm of nitrites, even after a 50 % water-change. I'm beginning to wonder about this.

A 50% water change will not make a big change if you really have 8 ppm nitrites and they now drop to 4 ppm - both could, on a kit, read about 5 ppm since the eye is not great at comparing colors since light type and intensity matters.

Do a real water change - 90%+ because nitrites should be well under 0.5 ppm or lower. That is a better test. I hope this isn't an aquarium with fish ... .

Knowledge is fun(damental)

A 75 gal with eight Discus, fake plants, and a lot of wood also with sand substrate. Clean up crew is down to just two Sterba's Corys. Filters: continuous new water flow; canister w/UV, in-tank algae scrubber!! Finally, junked the nitrate removal unit from hell.

+1 to Cermet. if you have to do multiple water changes to equal that 90 percent do so. I've had to do two fifty percent water changes at one time to get some of my NitrItes down. they were 3.0 at one point.

You aren't testing immediately after the w/c are you?
Anyway, do the math. If your nitrites are 20ppm to start, and you do 1 50% water change, that lowers it to 10ppm. Once more lowers it to 5ppm, once more to 2.5ppm etc.
You may need to do multiple w/c's.

I wait an hour after the water change to test, so far I've changed 150% of the water in three days. Still deep purple. Color tint never changes. Based on the theory that a 50% change drops the reading in half, I should have seen at least a small difference, I haven't.

As an experiment, take a store bought water bottle and test the water in it. If it gives a weird result there is a good chance your test kit may be messed up or expired.

Here is how to check the bottle to see if it is expired.

Each reagent bottle has a Lot # printed
on the bottle. The last four digits are the month and year of
manufacture. Example: Lot # 28A0102. This is a pH reagent manufactured
in January of 2002. Pond Care Wide Range pH, ammonia, High Range pH,
Nitrate, phosphate, Copper, calcium and GH all last for three years.
nitrite and KH will last for four years. Freshwater pH(low range) and
Pond Care Salt Level will last for five years. I would not trust these
kits after they have expired.